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LTE as an alternative to GSM-R
GSM-R is a communication technology designed for railways.
It provides two fundamental services:
railway digital signalling (the ETCS system)
and voice communication.
Why do we need an alternative to GSM-R?
Because it offers insufficient capacity
has low network utilization
and offers only limited support for
data services.
On the other hand
LTE offers packet-switched based transmission, which increases network utilization.
LTE introduces efficient radio interface
which results in flexible usage of spectrum and higher throughput.
Finally, packet delay in LTE is much lower,
what together with the increased throughput
allows LTE to support advanced real-time and interactive data services.
The shortcomings of GSM-R and the benefits of LTE
lead us to our main research question:
Can LTE become a railway communication technology?
This question consists of three challenges.
Firstly
can LTE support safety-critical ETCS signalling?
LTE needs to fulfil specific ETCS requirements
which concern parameters
such as: the received signal power
the message delay
and the delivery success rate.
There are three main elements which may affect ETCS transmission performance:
the train speed
the eNodeB density
and the traffic load.
The second challenge is voice communication,
which is still a very important service for railways.
Multiple solutions for providing voice communication
are still competing to become
the standard in LTE networks.
Compared to the commercial telephony
railways require additional voice functionality
such as: group calls
functional addressing, pre-emption and prioritization mechanisms.
The third challenge
is the Quality of Service.
In railway LTE network safety-critical and
best-effort applications
need to share resources.
Thus, efficient packet prioritization and pre-emption mechanisms are required.
How do we address these challenges?
Using OPNET simulations of the full LTE network.
OPNET allows to model and simulate an LTE network
which covers an exemplary real railway line.
LTE network is used here
to provide ETCS connectivity
between the LTE-equipped trains and the ETCS supervising servers.
Thanks to OPNET simulations
it is possible to collect various statistics
concerning ETCS performance.
We have already some outcomes concerning the performance of LTE
as a railway communication technology
Our first paper published in this field
presents an overview of the GSM-R shortcomings
as the motivation for the research on alternative technologies.
In our subsequent work we analyzed the ETCS performance in terms of
message delay and data integrity
in relation to the train speed.
The following research
analyzed the LTE radio access network
and how does it impact
the ETCS performance in terms of the message delay.
Finally, our latest results
concern the relation between the eNodeB density and the data
integrity of the ETCS messages.
If you are interested,
please do not hesitate on contacting us for discussion
or collaboration opportunities.
Thank you for your attention.